Speed Converter

How to Use the Speed Converter

Enter a numeric value in the input field and select your source unit from the dropdown. All five speed units update instantly: meters per second (m/s), kilometers per hour (km/h), miles per hour (mph), knots (kn), and feet per second (ft/s). The converter uses meters per second as the internal base unit for all calculations.

This tool is useful for comparing vehicle speeds between countries using different systems, converting wind speeds from weather reports, understanding aviation and maritime speeds given in knots, and solving physics problems that require speed in SI units.

Understanding Speed Units

Speed is distance divided by time. Each unit pairs a different distance measure with a time measure: m/s uses meters and seconds, km/h uses kilometers and hours, mph uses statute miles and hours, knots use nautical miles and hours, and ft/s uses feet and seconds. The relationships between these units come from the underlying distance and time conversions.

Key Conversion Factors

The most commonly needed factors are: 1 m/s = 3.6 km/h, 1 mph = 1.60934 km/h, 1 knot = 1.852 km/h, and 1 ft/s = 0.3048 m/s. For quick estimates: 100 km/h is about 62 mph, 60 mph is about 97 km/h, and 1 knot is about 1.15 mph. These approximations are handy for quick mental conversions when traveling.

When Each Unit Is Used

Meters per second is the SI standard used in physics and engineering. Kilometers per hour is standard for road speeds in most countries. Miles per hour is used for road speeds in the United States, United Kingdom, and a few other countries. Knots are the international standard for aviation and maritime navigation. Feet per second appears in ballistics, some engineering applications, and US-based physics problems.

Frequently Asked Questions

How do I convert km/h to mph?

Divide the speed in km/h by 1.609344 to get mph. For example, 100 km/h divided by 1.609344 equals approximately 62.14 mph. Alternatively, multiply km/h by 0.621371 for the same result. This conversion is essential when comparing vehicle speeds between metric and imperial countries.

How do I convert m/s to km/h?

Multiply the speed in m/s by 3.6 to get km/h. For example, 10 m/s times 3.6 equals 36 km/h. This works because there are 3,600 seconds in an hour and 1,000 meters in a kilometer, giving the factor 3600/1000 = 3.6.

What is a knot and how does it compare to mph?

A knot equals one nautical mile per hour, or approximately 1.15078 mph (1.852 km/h). Knots are used in aviation and maritime navigation because nautical miles relate directly to degrees of latitude, making navigation calculations simpler. One degree of latitude equals 60 nautical miles.

What is the speed of sound in different units?

The speed of sound in air at 20 degrees Celsius is approximately 343 m/s, 1,235 km/h, 767 mph, 667 knots, or 1,125 ft/s. This is known as Mach 1. The actual speed varies with temperature, humidity, and the medium through which sound travels.

Why is m/s the SI unit for speed?

Meters per second (m/s) is the SI unit because it is derived directly from the two base SI units: the meter for distance and the second for time. Using base units keeps scientific equations consistent and avoids conversion factors in formulas like kinetic energy (KE = 0.5mv^2) and momentum (p = mv).